U.S. patent number 7,474,681 [Application Number 11/245,255] was granted by the patent office on 2009-01-06 for alternating current light-emitting device.
This patent grant is currently assigned to Industrial Technology Research Institute. Invention is credited to Sheng-Pan Huang, Ming-Te Lin, Ming-Yao Lin, Wen-Yung Yeh, Hsi-Hsuan Yen.
United States Patent |
7,474,681 |
Lin , et al. |
January 6, 2009 |
Alternating current light-emitting device
Abstract
An alternating current light emitting device and the fabrication
method includes forming one or more alternating current micro diode
light emitting modules on a substrate, wherein the alternating
current micro diode light emitting module has two micro diodes
connected to one another, and each micro diode has at least two
active layers and is electrically connected by a conductive
structure, such that the active layers of each micro diode can take
turns emitting light during the positive/negative half cycles of
alternating current. A continuous and full-scale light emitting
effect is thereby achieved.
Inventors: |
Lin; Ming-Te (Hsinchu Hsien,
TW), Yen; Hsi-Hsuan (Hsinchu Hsien, TW),
Yeh; Wen-Yung (Hsinchu Hsien, TW), Lin; Ming-Yao
(Hsinchu Hsien, TW), Huang; Sheng-Pan (Hsinchu Hsien,
TW) |
Assignee: |
Industrial Technology Research
Institute (Hsinchu, TW)
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Family
ID: |
37419068 |
Appl.
No.: |
11/245,255 |
Filed: |
October 7, 2005 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060256826 A1 |
Nov 16, 2006 |
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Foreign Application Priority Data
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May 13, 2005 [TW] |
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94115514 A |
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Current U.S.
Class: |
372/43.01;
250/221; 250/551; 257/E25.02; 372/45.01; 372/96 |
Current CPC
Class: |
H01L
25/0753 (20130101); H01L 27/156 (20130101); F21K
9/00 (20130101); H01L 33/62 (20130101); H01L
2924/0002 (20130101); H01L 2924/0002 (20130101); H01L
2924/00 (20130101) |
Current International
Class: |
H01S
5/00 (20060101) |
Field of
Search: |
;372/50.1,50.12,50.121,68,43.01,45.01,96 ;250/221,551 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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219086 |
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Feb 1985 |
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DD |
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10103422 |
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Aug 2002 |
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DE |
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5198843 |
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Aug 1993 |
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JP |
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07263752 |
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Oct 1995 |
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JP |
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10256597 |
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Sep 1998 |
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JP |
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2004-333583 |
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Nov 2004 |
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JP |
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200501464 |
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Jan 2005 |
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TW |
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WO 2004023568 |
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Mar 2004 |
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WO |
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WO 2006030734 |
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Mar 2006 |
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WO |
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Primary Examiner: Harvey; Minsun
Assistant Examiner: Zhang; Yuanda
Attorney, Agent or Firm: Finnegan, Henderson, Farabow,
Garrett & Dunner LLP
Claims
What is claimed is:
1. An alternating current light emitting device comprising: a
substrate; a bridge light-emitting unit formed on the substrate
including: a plurality of alternating current light emitting micro
diodes wherein each alternating current light emitting micro diode
has at least one active layer, active layers of a first group of
the alternating current light emitting micro diodes being arranged
on four peripheral arms of a bridge rectifier, active layers of a
second group of the alternating current light emitting micro diodes
being arranged on a connecting arm connecting first and second
diagonally opposed corners of the bridge rectifier, and first and
second unit conductive electrodes being disposed at third and
fourth diagonally opposed corners of the bridge rectifier,
respectively for connecting with alternating current; and a
conductive structure electrically connected to each of the
alternating current light emitting micro diodes so as to allow the
active layers of the first group of the alternating current light
emitting micro diodes to alternately emit light during positive and
negative half cycles of alternating current and allow the active
layers of the second group of the alternating current light
emitting micro diodes to emit light during both positive and
negative half cycles of alternating current.
2. The alternating current light emitting device of claim 1,
wherein the first unit conductive electrode, the second unit
conductive electrode and the active layers of the alternating
current light emitting micro diodes are electrically coupled to
each other for connecting with alternating current.
3. The alternating current light emitting device of claim 1 further
comprising a plurality of the bridge light-emitting units, wherein
the plurality of the bridge light-emitting units are electrically
coupled to each other.
4. The alternating current light emitting device of claim 3,
wherein the plurality of the bridge light-emitting units are
arranged in a matrix.
5. The alternating current light emitting device of claim 1,
wherein the substrate comprises an insulating substrate.
6. The alternating current light emitting device of claim 1,
wherein each active layer of the alternating current light emitting
micro diodes emits light of identical wavelengths.
7. The alternating current light emitting device of claim 1,
wherein at least each of the second group of alternating current
light emitting micro diodes has at least two active layers, each
active layer emitting light of different wavelengths.
8. The alternating current light emitting device of claim 3 further
comprising first and second matrix conductive electrodes, wherein
the first and second conductive electrodes are electrically coupled
to the plurality of the bridge light-emitting units for connecting
with alternating current.
9. The alternating current light emitting device of claim 8,
wherein the first and second matrix conductive electrodes are
disposed at first and second diagonally opposed corners of the
matrix respectively.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light-emitting device, and more
particularly, to an alternating current light emitting device and
the fabrication method thereof.
2. Description of Related Art
Unlike white light which is a mixture of different colors, light
emitting diodes (LEDs) emit monochromatic light by applying
electric current to a radiating material to produce a light
described as a cold light since it is produced at a relatively low
temperature. Due to the superiority of light emitting diodes in
terms of their relative high durability, longevity, portability,
low power consumption, absence of harmful substances such as
mercury, and so forth, the development of LED-based solid state
lighting has become one of the crucial research targets for the
global lighting industry as well as the semiconductor industry.
Often-seen applications of LEDs include white light illumination
(using red, blue, and green LEDs), indicator lights, vehicle signal
and illuminating lights, flash lights, LED back-light modules,
projector light sources, outdoor displays, and so forth.
White light devices, among the most important lighting
applications, still require a patented fabrication process
involving fluorescent light. In addition to the necessity of paying
royalties, drawbacks include the distribution ratio of fluorescent
light and the high color temperature of white light generated by a
packaging fabrication process that can lead to decreased operating
life and loss of efficacy as a result of the high temperature.
Moreover, difficulties in controlling the conventional packaging
technique lead to low yield.
Taiwanese Patent Application No. 093126201 discloses a light
emitting diode (LED) chip structure having an alternating current
circuit, the patent comprising at least one alternating current
micro diode LED module formed on a chip and comprised of two micro
diode LEDs having a reverse positive/negative parallel connection
so as to apply alternating current thereto, such that two micro
diode LEDs can, working in turn, emit light during both the
positive and negative half cycles of the AC waveform to overcome
the drawback of the prior art technique in which devices utilizing
that technique emit light during only the positive half cycle but
not during the negative half cycle. The invention thereby achieves
the objective of fully utilizing alternating current as a power
source to significantly expand and upgrade applications of LED
elements.
In the foregoing patent, due to the plane array configuration
adopted, each micro diode can only emit light during an alternating
current half cycle in which the current is flowing in the same
direction. In other words, at any particular moment, only half the
area of the chip surface can emit light and micro diodes on the
other half of the chip surface are non-luminous in an off status.
Therefore, in order to obtain the same amount of light that could
be obtained if the device constantly emitted light during both half
cycles, the amount of electric current has to be doubled.
Further, the micro diode disclosed by said patent has an isosceles,
right-angle triangular shape with legs of an approximate length of
70 micrometers each. The design process is difficult if it is
necessary to reduce the size of the LEDs to comply with the
application trend for product miniaturization. Furthermore, since
this patent requires the application of patented sun-second
fluorescent powder, the foregoing drawbacks of high color
temperature and a hard-to-control packaging process still
exist.
Therefore, a need exists to develop a novel alternating current
light emitting device that not only improves on the drawbacks of
the prior art, but also provides a full-scale light emitting area
so as to evenly emit light full time in a way that can be
controlled at low color temperature while also exhibiting a higher
overlapping area without requiring the use of patented sun-second
fluorescent power, thereby decreasing the fabrication difficulties
and increasing yield to further enhance the industrial
applicability.
SUMMARY OF THE INVENTION
The present invention is accomplished in order to improve the
shortcomings disclosed in the prior art. A primary objective of the
present invention to provide a novel alternating current light
emitting device and the fabrication method thereof that has a full
scale light emitting area and also can emit light full time.
Another objective of the present invention is to provide a novel
alternating current light emitting device and the fabrication
method thereof without requiring the application of patented
fluorescent powder.
Another objective of the present invention is to provide a novel
alternating current light emitting device and the fabrication
method thereof that has a reduced size.
Another objective of the present invention is to provide a novel
alternating current light emitting device that can emit light more
evenly.
To achieve the above and other objectives, the present invention
provides an alternating current light emitting device, the device
comprising: a substrate; an alternating current micro diode light
emitting module formed on the substrate having at least two micro
diodes, each micro diode having at least two active layers; and a
conductive structure electrically connected to each micro diode,
allowing the active layers of each micro diode to take turns
emitting light during the positive and negative half cycles of
alternating current.
The foregoing substrate can be a chip or an insulating substrate.
The active layer is a luminescent active layer. The conductive
structure at least comprises a conductor connecting the two micro
diodes such as a conductive bridge network.
Each micro diode and the active layer thereof are electrically
connected by a series connection and a parallel connection. Each
micro diode can emit light at the same wavelength to thereby emit
light of identical colors (monochromatic light), or can emit light
at different wavelengths to produce mixed light (multichromatic
light). Preferably, each active layer of the micro diode can emit
different wavelengths in order to form white light by mixing colors
together or form various hues by a combination thereof. Based on
the variations of the combination, the same active layer of each
micro diode can take turns to emit light during the
positive/negative half cycles of alternating current.
Alternatively, the different active layers of each micro diode can
also take turns to emit light during the positive/negative half
cycles of alternating current.
In addition, each micro diode formed on the substrate having at
least two active layers can be accomplished by a Flip-Chip, wafer
bonding or chip-stacked technique.
To achieve the above and other objectives, the present invention
further provides a novel alternating current light emitting device,
the device comprising: a substrate; a plurality of alternating
current micro diode light emitting modules formed on the substrate,
each alternating current micro diode light emitting module having
at least two micro diodes, and each micro diode having at least two
active layers; and a conductive structure electrically connected to
each alternating current micro diode light emitting module and each
micro diode so as to cause the active layers to take turns emitting
light during the positive and negative half cycles of alternating
current.
As described above, at least one active layer of the micro diode is
arranged as per the circuit structure of the diodes in a bridge
rectifier, and is electrically connected to form one or more bridge
light-emitting units. Additionally, the bridge light emitting units
can be arranged in the rectangular shape of a matrix, and the
number of light emitting units disposed in the central region can
be larger than the number of light emitting units disposed in the
peripheral regions. Preferably, the arrangement scheme can further
comprise disposing the conductive electrodes on the two diagonals
of the matrix, and the conductive electrodes and the bridge light
emitting units are serially connected to each other for connecting
with alternating current.
In accordance with the foregoing, the present invention further
provides two fabrication methods for the alternating current light
emitting devices disclosed by the present invention. The first
method comprises the steps of: preparing a substrate; forming at
least two active layers on the substrate; forming a plurality of
openings on each active layer respectively; covering the outer
periphery of the active layer with a protective layer; forming a
plurality of conductive terminals through the protective layer to
electrically connect to the active layer; and, lastly, forming a
plurality of conductive structures on the openings so as to
electrically connect to each active layer, such that application of
alternating current to each of the active layers during usage will
cause them to take turns emitting light during the positive and
negative half cycles of the alternating current.
The second method comprises the steps of: preparing a first
substrate; forming a first active layer on the substrate and
removing the first substrate and disposing the first active layer
on a second substrate; forming a second active layer on the first
active layer and forming a connective layer between the first
active layer and the second active layer; forming a plurality of
openings on the first active layer and the second active layer;
covering the outer periphery of the first active layer and the
second active layer with a protective layer; forming a plurality of
conductive terminals through the protective layer; and, lastly,
forming a plurality of conductive structures on the openings so as
to electrically connect to the first active layer and the second
active layer, such that application of alternating current to the
first active layer and the second active layer during usage will
cause them to take turns emitting light during the positive and
negative half cycles of alternating current.
Additionally, the present invention further provides another
alternating current light emitting device, the device comprising:
at least a substrate; a bridge light-emitting unit including a
plurality of alternating current light emitting diode micro diodes
formed on the substrate, the micro diodes being arranged based on
the circuit structure of the diodes in a bridge rectifier; and a
conductive structure electrically connected to the micro diodes so
as to cause them to take turns emitting light during the positive
and negative half cycles of alternating current. Preferably, the
light emitting device can include a plurality of bridge light
emitting units electrically connected to one another, each bridge
light emitting unit being arranged in a matrix, wherein the number
of the light emitting units disposed in the central region is
larger than the light emitting units disposed in the peripheral
areas, thereby providing a full-scale light emitting area and an
even light emitting effect. Additionally, the light emitting device
can include disposing conductive electrodes on the two diagonals of
the matrix, the conductive electrodes each being serially connected
to each bridge light emitting unit for providing alternating
current.
Further scope of the applicability of the present invention will
become apparent from the detailed description given hereinafter.
However, it should be understood that the detailed description and
specific examples, while indicating preferred embodiments of the
invention, are given by way of illustration only, since various
changes and modifications within the spirit and scope of the
invention will become apparent to those skilled in the art from
this detailed description.
BRIEF DESCRIPTION OF DRAWINGS
The various objectives and advantages of the present invention can
be fully understood by reading the following detailed description
with reference made to the accompanying drawings, which are given
by way of illustration only, and thus are not limitative of the
present invention, and wherein:
FIGS. 1A and 1B are, respectively, a schematic sectional view and a
partially enlarged view of an alternating current light emitting
device according to the present invention;
FIGS. 2A and 2B are schematic views illustrating the operation of a
preferred embodiment of the alternating current light emitting
device according to the present invention;
FIGS. 3A and 3B show the respective circuitry of FIGS. 2A and 2B
illustrating the operation of a preferred embodiment of the
alternating current light emitting device according to the present
invention;
FIG. 4 is a bottom view showing the application of a plurality of
the alternating current light emitting devices to a chip according
to the present invention;
FIGS. 5A and 5B are schematic views showing the operation of the
alternating current light emitting device of another preferred
embodiment according to the present invention;
FIGS. 6A and 6B show the respective circuitry of FIGS. 5A and 5B
illustrating the operation of another preferred embodiment of the
AC light emitting device according to the present invention;
FIG. 7 is a three-layer equivalent circuitry showing a plurality of
the alternating current light emitting devices of the present
invention;
FIG. 8 shows the basic circuitry showing the micro diodes of the
plurality of the alternating current light emitting devices of the
present invention having at least one active layer with diodes
being arranged according to the circuit configuration diodes in a
Bridge Rectifier.
FIGS. 9A and 9B are, respectively, schematic diagrams showing the
application of each half cycle of alternating current to a chip
according to the circuit configuration of the preferred embodiment
depicted in FIG. 8;
FIGS. 10A and 10B are, respectively, schematic diagrams showing the
application of each half cycle of alternating current of half waves
to a bridge rectifier with a plurality of bridge light emitting
units to a chip using the circuit configuration of the preferred
embodiment depicted in FIG. 8;
FIGS. 11A through 11E are structural flowcharts showing,
collectively, a fabrication method of the alternating current light
emitting devices of the present invention; and
FIG. 12A through 12F are structural flowcharts showing,
collectively, another fabrication method of the alternating current
light emitting devices of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention discloses an alternating current
light-emitting device applicable to a chip, the alternating current
light-emitting device being capable of generating white light or
colored light by externally generated alternating current power,
the invention being capable of emitting the white light or colored
light full time from the light-emitting surface of the chip,
wherein the preferred implementation mode is the general market
power according to the universal power standards, the voltage being
110V or 220V and the frequency being 60 Hz or 50 Hz.
FIGS. 1A and 1B each show a cross-sectional view of the structure
of the alternating current light-emitting device of the present
invention. The drawings depict only one single alternating current
light-emitting device in this preferred embodiment. The alternating
current light-emitting device at least comprises a substrate 1, an
alternating current micro diode light emitting module 2 formed on
the substrate 1, and a conductive structure 3 for providing an
electrical connection.
In this preferred embodiment, the substrate 1 can be the chip as
mentioned above, or an insulating substrate, such as
Al.sub.2O.sub.3, GaAs, GaP, SiC, and so forth.
FIG. 1B is enlarged to clearly illustrate the alternating current
micro diode light emitting module 2, which comprises at least two
micro diodes 20a and 20b which each further comprises at least two
active layers, namely, the upper Active layers 200a and 200b and
the lower active layers 201a and 201b as shown in the drawing,
wherein the active layers are light-emitting active layers, and
each active layer of micro diodes 20a and 20b comprises individual
ohm electrodes 202a, 202b, 203a, 203b, 204a, 204b, 205a and 205b,
such that the active layer can emit light by limiting alternating
current by means of these ohm electrodes 202a, 202b, 203a, 203b,
204a, 204b, 205a and 205b. In addition, each micro diode formed on
the substrate 1 having at least two active layers can be
accomplished by a Flip-Chip, wafer bonding or chip-stacked
technique.
The conductive structure 3 is electrically connected to micro
diodes 20a and 20b, such that the active layers can take turns to
emit light during the positive/negative half cycles of alternating
current, wherein the conductive structure 3 at least comprises a
conductive body 30b connected between the two micro diodes, as
shown in FIG. 1A, the conductive structure 3 further including
conductive bodies 30a and 30c for connecting with alternating
current, and, in this embodiment, the conductive bodies 30a, 30b,
and 30c are preferably a conductive bridge.
The operation of the alternating current light-emitting device of
the invention will be described in the following preferred
embodiments with reference to FIGS. 2A and 2B and FIGS. 3A and 3B.
FIGS. 2A and 2B show the status of the alternating current
light-emitting device being applied with alternating current. FIGS.
3A and 3B are equivalent circuitry of the alternating current
light-emitting device, each respectively corresponding to FIGS. 2A
and 2B, wherein each active layer is composed of an upper active
layer 200 and a lower active layer 201 that are equivalent to light
emitting diodes having a P/N structure, thereby forming a serial
connection between the upper active layer 200 and the lower active
layer 201 of each micro diode 20, and between each of the micro
diodes 20 that are electrically connected by the conductive
structure 3, as shown in FIGS. 3A and 3B.
FIGS. 2A and 3A each show the radiant status while the positive
half cycle of alternating current flows through the alternating
current light emitting device. When inputting the positive half
cycle of alternating current thereto, the LED structure composed of
the upper active layers 200 of the micro diodes 200 is forward
biased, and the positive half cycle of current, as shown in an
arrow of FIG. 3A, enables the upper active layers 200 to emit light
through the upper active layer 200 of micro diodes 20. Similarly,
when inputting the negative half cycle of alternating current
thereto, the LED structure composed of the lower active layers 201
of micro diodes 200 is forward biased, and the negative half cycle
of current, as shown in an arrow of FIG. 3B, enables the lower
active layers 201 to emit light through the lower active layer 201
of micro diodes 20. In other words, as can be seen from the
equivalent circuitry, the invention is implemented by using two
equivalent light emitting diodes (LEDs) overlapping one another for
receiving the positive/negative half cycles of alternating current,
thereby enabling the alternating current light-emitting device of
the invention to emit light when both the positive half cycles and
negative half cycles of alternating current flow through the
device, and also enabling the same active layers of micro diodes 20
(upper active layer 200 or lower active layer 201) to take turns to
emit light by means of the positive and negative half cycles of
alternating current.
As shown in FIG. 4, when a plurality of the alternating current
light-emitting devices of the invention interlacing one another are
staggered and arranged on a chip and applied with alternating
current, the light-emitting surface of the chip can take turns to
emit light using, for example, a 60 Hz frequency, wherein the micro
diodes can have the same or different wavelengths to emit light of
the same or different colors (the light being produced in the
active layers). If different wavelength characteristics are
selected for the micro diodes 20 such that, for example, the upper
active layer emits green light and the lower active layer emits red
light, then alternating light-emitting of the upper active layer
and the bottom active layer can have the effect of mixing light
(red light and green light). More specifically, if green light
having a wavelength of 485 to 500 nm (for the upper active layer)
is used together with red light having a wavelength 580 to 620 nm
(for the lower active layer), the interlacing and twinkling light
emitted by the upper active layer and the lower active layer is
mixed to have an effect similar to white light overlapped with
black radiant curves. Accordingly, the present invention not only
provides an improved light-emitting device that can emit light
continuously, but also provides a device that can be adjusted so as
to selectively emit a monochromatic light or mixed colors of light
according to the user's implementation and requirements, thereby
eliminating the necessity of using fluorescent powder to produce
white light. Therefore, the present invention offers advantages
over the prior art technique.
FIGS. 5A and 5B illustrate another application of the alternating
current light-emitting device of the invention and the equivalent
circuitry thereof shown in FIGS. 6A and 6B, wherein each active
layer (comprised of upper active sub-layers 200c and 200d and lower
active sub-layers 201c and 201d) is an equivalent to a light
emitting diode (LED) having a P/N structure (wherein upper active
sub-layers 200c and 200d are of a P structure and lower active
sub-layers 201c and 201d are of an N structure), thereby making
upper active layers 200c and 200d and lower active layers 201c and
201d of micro diodes 20c and 20d serially connected while the
conductive structure 3 is electrically connected to micro diodes
20c and 20d in parallel connection.
FIG. 5A and FIG. 6A each illustrate the radiating status of the
alternating current light-emitting device during the positive half
cycle of alternating current. During the positive half cycle of
alternating current, different active layers of the adjacent micro
diodes 20c and 20d are forward biased (namely, the upper active
layer 200c of the micro diode 20c and lower active layers 201d of
the micro diode 20d). The positive half cycle of alternating
current as shown by an arrow in FIG. 6A passes through different
active layers of micro diodes 20c and 20d to enable each different
active layer to emit light. Similarly, during the negative half
cycle of alternating current as shown in FIG. 5B and FIG. 6B,
different active layers of the adjacent micro diodes 20c and 20d
are forward biased (namely, upper active layers 200d of the micro
diode 20d and the lower active layers 201c of the micro diode 20c).
The negative half cycle of alternating current as shown by an arrow
in FIG. 6B passes through different active layers of micro diodes
20c and 20d to enable each different active layer to emit light. In
other words, as it can be seen from the equivalent circuitry, the
preferred embodiment is implemented using two identical light
emitting diodes stacked together in an upper/lower manner for
receiving the positive/negative half cycles of alternating current,
such that the alternating current light-emitting device of the
invention can emit light when either the positive or negative half
cycles of alternating current are applied thereto. It differs from
the applications depicted in FIGS. 2A, 2B, 3A and 3B in that the
different active layers of the micro diodes 20c and 20d take turns
to emit light during the positive/negative half cycles of
alternating current. A plurality of alternating current light
emitting devices employed in this embodiment are interlacingly
arranged on a chip to receive alternating current that empowers the
light emitting surface of the chip to emit light continuously.
Similarly, the micro diodes 20c and 20d as described above can have
the same or different wavelengths (each active layer can also have
the same or different wavelengths) in order to emit light of
identical or different colors, wherein if micro diodes 20c and 20d
emit different wavelengths, such as the upper active layers 200c
and 200d emit green light and the bottom active layers 201c and
201d emit red light, the alternating of the light emitting from the
different active layers (upper active layer 200c--bottom active
layer 201d or upper active layer 200d to bottom active layer 201c)
can achieve the effect of mixing colored light (such as red light
plus green light, the application thereof is the same as the
foregoing embodiment and thus will not be further detailed herein).
Additionally, since the upper active layers 200c and 200d and the
bottom active layers 201c and 201d are capable--depending on
fabrication--of emitting light of different colors at a pulsating,
light-emitting frequency of 120 Hz (60 Hz.times.2) that practically
exceeds the highest frequency 100 Hz that is recognizable by human
vision, then this has the visual effect of mixing light more evenly
or softly to provide for an optimal visual effect. Accordingly, the
continuous light emitting device employed in this embodiment not
only can comply with users' needs to flexibly allocate colors of
emitting light but also can produce more even and soft light for
optimal visual effects.
In the case that the alternating current light emitting device of
the present invention is a structure having three active layers--a
preferred embodiment shown in FIG. 7 illustrates an equivalent
circuitry adding one active layer as described above and one
equivalent light emitting diode--more colors are possible. When
inputting the positive half-cycle of alternating current as shown
by an arrow, each active layer conducting the positive half-cycle
of current will emit light (the current passing route of the
negative half-cycle of alternating current can be easily discerned
from the positive half-cycle of current and thus is not further
detailed herein). A preferred embodiment of this three-layer
structure is implemented by having a first layer L1 to emit green
light that is the most essential color for producing white light
due to the way the human eye poorly responds to light of green
frequency, having a second layer L2 to emit blue light that is the
next most essential color for producing white light, and having a
third layer L3 to emit red light that is the third most essential
color for producing white light. Based on FIG. 7, the colors
produced during the positive half cycle of alternating current
appear in the order (following the arrow from left to right) of
blue, green, green, red, blue, green, green, red. The colors
produced during the negative half cycle of alternating current also
appear in the same order of blue, green, green, red, blue, green,
green, red, but this time current flows from right to left to
utilize the two blue and two red diodes that didn't conduct during
the positive half-cycle (all of the green diodes emit light during
the negative half-cycle just as during the positive half-cycle
since, as mentioned, the human eye needs more green mixed in order
to perceive white). Therefore, the alternating current light
emitting device of the invention can employ and match different
colors to achieve an overall desired color effect when the positive
or negative half cycles of alternating current are applied to the
active layers thereof. Also, in order for this three-layer
structure to have the effect of producing white light (by mixing
colors of emitted light), a preferable application is to mix green
light at a 535 nm wavelength with blue light at a 460 nm wavelength
and red light at a 630 nm wavelength. It should be added that when
three or more active layers are used to mix light, adjustments in
color temperature are required, for example, one or more active
layers can be made nonluminous by applying short circuits to meet
the light mixing requirements in practical use.
Furthermore, as shown in FIG. 8, the one or more active layers of
the micro diode disclosed in the invention can be configured using
the circuit structure of diodes configured in a bridge rectifier
configuration, wherein each active layer is electrically connected
(one active layer as described above that is an equivalent of a
light emitting diode). An optimal application of this light-mixing
effect is to mix colors of two or three layers (wherein the
preferred color mixing applications for two or three layers are the
same as that described above and thus will be omitted herein).
Also, as illustrated in FIG. 8, each of the electrically connected
circuits arranged as per the foregoing circuit structure is defined
as a first circuit C1, a second circuit C2, a third circuit C3, a
fourth circuit C4 and a fifth circuit C5 for illustration purposes,
wherein the light emitting colors and number of each active layers
(an equivalent to a light emitting diode) can be decided by the
users depending on the requirements. A preferred embodiment is to
respectively dispose 10 active layers of the micro diodes on the
first circuit C1, the second circuit C2, the fourth circuit C4, and
the fifth circuit C5, and disposing 22 active layers of the micro
diodes on the third circuit C3, wherein each alternating current
light emitting micro diode has one or more active layers. The
number of the active layers taking the alternating current reverse
bias voltage in this kind of circuit structure arrangement is about
half of the number of the active layers taking the alternating
current forward bias voltage, therefore, if this structure uses a
plurality of active layers to concurrently take the reverse bias
voltage of alternating current, the reverse bias alternating
current voltage will be evenly absorbed (one active layer can take
about 10-15 volts of reverse bias voltage) so as to prevent
shorting or break-down that may occur due to breaking the active
layers from excessive reverse bias voltage. Also, the foregoing
embodiment can be implemented to achieve the effect of mixing
colors to produce white light. The figure showing this embodiment
is characterized in that, in addition to the fact that light
emitting diodes differing colors may be used and that the number of
the active layers can be flexibly decided, the configuration of the
second circuit C2, the third circuit C3 and the fourth circuit C4
as shown in FIG. 9A conducting the positive half cycle of
alternating current, and the configuration of the fifth circuit C5,
the third circuit C3 and the first circuit C1 conducting the
negative half cycle of alternating current as shown in FIG. 9B, are
employed to dispose the third circuit to conduct both the positive
and negative half cycles of alternating current on the light
emitting surface of a chip, thereby achieving the effect of
continuous light emitting when the conductive electrodes E1 and E2
on the major light emitting area of the chip surface are connected
with alternating current (said conductive electrode E1 and E2 are
electrically connected to the circuit). As the plurality of active
layers of the micro diodes of the third circuit C3 can emit light
during either the positive or negative half cycles of alternating
current, the number of active layers used in prior art techniques
can be reduced. For example, the number of active layers used in
prior art techniques requires 22 layers for each of the positive
and the negative half cycles of alternating current, making a total
number of 44, while, in the present invention, only a total number
of 22 active layers are required to achieve the effect of
continuous light emitting;
Furthermore, the circuit configuration of the foregoing active
layers (equivalent to LEDs) of the micro diode can also be a bridge
light-emitting unit B1 as shown in FIG. 8, that is, one or more
active layers of a micro diode of a bridge light-emitting unit B1
is arranged as per the diodes in a bridge rectifier to electrically
connect to one another. A plurality of bridge light-emitting units
B1 arranged in a matrix as shown in FIGS. 10A and 10B is disposed
on the light emitting surface of a chip, the two diagonal corners
of the matrix being disposed with two conductive electrodes E3 and
E4 for connecting with alternating current (the two conductive
electrodes E3 and E4 being serially connected with the bridge
light-emitting unit B1), such that when connected to alternating
current, the current of the positive or negative half cycles passes
through most parts of the light emitting surface of the chip to
emit light continuously;
The circuit configuration as described above can also be applied to
an alternating current light emitting device composed of micro
diodes having a single active layer, such as forming bridge light
emitting units composed of a plurality of alternating current light
emitting diodes on a substrate, the circuit configuration of micro
diodes being arranged as per the diodes in a bridge rectifier and
being electrically connected to each micro diode through a
conductive structure, thereby making the micro diodes to take turns
to emit light during the positive and negative half cycles of
alternating current. Alternatively, it can include a plurality of
bridge light emitting units electrically connected to one another,
each bridge light emitting unit being disposed as a part of a
matrix, wherein the number of the bridge light emitting units in
the central region is larger than that in the peripheral region to
thereby achieve a continuous and more even light emitting effect.
Additionally, it further includes a step of disposing two
conductive electrodes on the two diagonal corners of the matrix,
each conductive electrode being serially connected to each bridge
light emitting unit to provide connection of alternating current.
Since the circuit structure thereof is similar to that described
above, thus it will not be further detailed herein.
The active layers (an equivalent to a LED as mentioned above)
disclosed by the present invention do not require any
externally-added load in order to apply AC power directly to the
relative circuits of the blocking or indicating circuits, and also
it can have a plurality of active layers being in configured in a
parallel connection and then can be serially connected to each
other so as to have different lighting applications. Moreover, the
active layers can be applied to LCD Backlight devices as disclosed
by USP 2005001537, USP 2004246696, and JSP 2004333583. The active
layers can also be implemented by a variety of manufacturing
processes, such as the 5 LED conducting wire stand glue-irrigating
packaging process; the Super Flux conducting wire stand
glue-irrigating packaging process; the Flip-Chip, ceramics and
aluminum substrate manufacturing processes; the PPA point-gluing,
injection packaging process; or the To metal shell packaging
process, and so forth.
The present invention further provides a fabrication method for the
alternating current light emitting device as shown in FIGS. 11A
through 11E. To correspond with the aforementioned embodiments, the
fabrication method thereof is exemplified by the drawing depicting
two alternating current light emitting devices. Referring to FIG.
11A, the fabrication method comprises the steps of: preparing a
substrate 1 and forming at least two active layers on the substrate
in a chip-stacking manner (an upper active layer 200 and a lower
active layer 201 as shown in the drawing), wherein the active layer
is a connected p-type light emitting layer with a n-type light
emitting layer that, collectively, are equivalent to the light
emitting diode P/N structure, the p-type light emitting layer and
the n-type light emitting layer are preferably implemented using
P-InGaN and N-InGaN respectively. Subsequently, as shown in FIG.
11B, a plurality of openings 4 is formed on the active layer (upper
active layer 200 and bottom active layer 201) by yellow light
shadowing and etching techniques to expose the substrate 1. Then,
as shown in FIG. 11C, the outer periphery of the active layer
(upper active layer 200 and lower active layer 201) is covered by a
protection layer 5 for preventing leakage of current, the
protection layer 5 being composed of dielectric materials, such as
SiO.sub.x or SiN.sub.x, and so forth. Following that, as shown in
FIG. 11D, a plurality of conductive terminals 6a, 6b, 6c, and 6d is
formed through the protection layer 5 so as to electrically connect
to the active layer (upper active layer 200 and lower active layer
201). Lastly, as shown in FIG. 11E, a plurality of conductive
structures 3 is formed on the openings 4 to electrically connect to
the active layers (upper active layer 200 and lower active layer
201) so as to enable them to take turns to emit light during the
positive or negative half cycles of alternating current. As the
application of substrate 1, the active layers (upper active layer
200 and lower active layer 201), and the conductive structure 3
mentioned in the fabrication method is same as those shown in FIGS.
2A, 2B, 3A, and 3B, therefore the description thereof will be
omitted herein.
The plurality of conductive terminals 6a, 6b, 6c, and 6d is formed
by means of steam-gilding and can be implemented using an Ohm
electrode electrically connected to the active layers (upper active
layer 200 and lower active layer 201) to form a micro diode 20,
which can be implemented by having identical or different
wavelengths as mentioned above.
Accordingly, FIGS. 12A through 12F illustrate a fabrication method
of the alternating current light emitting device of the present
invention using two alternating current light emitting devices in
accordance with the aforementioned embodiments. The method
comprises the steps of: preparing a first substrate (not shown),
forming a first active layer 70 on the first substrate, and
removing the first substrate; then, referring to FIG. 12A, the
first active layer 70 is disposed on a second substrate 8, and,
further referring to FIG. 12B, a second active layer 71 is formed
on the first active layer 70 with a connection layer 72 formed
between the first active layer 70 and the second active layer 71,
the connection layer being made of conductive and non-conductor
materials and is pervious to light; then, referring to FIG. 12C, a
plurality of openings 9 is formed on the first active layer 70 and
the second active layer 71 by yellow-light development and etching
techniques so as to expose the second substrate 8; then, referring
to FIG. 12D, a protective layer 10 is applied on top of the outer
peripheral region of the first active layer 70 and the second
active layer 71 to prevent leakage of electric current, the
protective layer 10 being made of dielectric materials such as
SiO.sub.x, SiN.sub.x and so on; then, further referring to FIG.
12E, a plurality of conductive terminals 6e, 6f, 6g, and 6h is
formed through the protective layer 10 to electrically connect to
the first active layer 70 and the second active layer 71; lastly,
referring to FIG. 12F, a plurality of conductive structures 3 is
formed on the openings 9 to electrically connect to the first
active layer 70 and the second active layer 71 so as to enable the
structure to take turns to emit light via the positive or negative
half cycles of alternating current. As the second substrate 8,
active layers (the first active layer 70 and the second active
layer 71) and the conductive structures 3 are substantially similar
in structure to those embodiments described in FIGS. 2A, 2B, 3A,
and 3B, thus they will not be further detailed herein.
Similarly, the plurality of conductive terminals 6e, 6f, 6g, and 6h
is formed by the same steam-gilding technique as the foregoing
method and is implemented using an Ohm electrode to electrically
connect to the active layers (the first active layer 70 and the
second active layer 71) to form a micro diode 20 that can have the
same or different wavelengths.
In summary of the above, the alternating current light emitting
device disclosed by the present invention is characterized in that
each micro diode formed is comprised of at least two active layers
(preferably two or three layers), such that each active layer of
the micro diode can take turns to emit light during the positive or
negative half cycles of alternating current, thereby possessing a
full-scale and continuous light emitting characteristic.
Furthermore, the structural application of the active layers
disclosed by the present invention can be applied to different
circuit configurations to achieve the optimal effect of mixing
light and continuous light emission as required.
The present invention has been described using the foregoing
exemplary preferred embodiments. All modifications and variations
of equal functions without violating the principle and technology
of the present invention should be included in the scope of the
claims to be described below.
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